This invention relates to a music box rotating drum body constituted by a metallic pipe material.
In FIG. 1, a bottomed cylinder-shaped box 2, in which a spiral spring serving as a music box driving source and drive gears rotationally driven by the spiral spring are housed, is fixed at a corner portion of a rectangular music box frame 1 with the bottom of the box placed upward. A rotating drum body 3 rotationally driven by the drive gears on the basis of the accumulated force of the spiral spring is supported on the frame 1 by a shaft. Further, a base portion of a diaphragm 7 having a large number of vibrating valves formed in the order of musical scales is fixed on the frame 1. Forward ends of the respective vibrating valves in the diaphragm 7 are arranged opposite to the circumferential surface of the rotating drum body 3. When the rotating drum body 3 is driven to rotate, forward end portions of vibrating valves are flicked by pins (not shown) formed on the circumferential surface of the o rotating drum body 3 to thereby play a predetermined music program.
The rotating drum body 3 comprises a rotating drum 4, and holding members 5 and 6 (constituted by gears or end plates) stuck to opposite ends of the rotating drum 4 so as to be fitted thereto to rotatably hold the rotating drum 4.
A rotating drum body produced by forming holes in a metallic pipe material and driving pins into the holes is one type of music rotating drum body.
A brass pipe material is used as the pipe material in which pins are driven into holes formed by drilling or the like in positions in accordance with the music program.
Further, in the music box rotating drum body, a silent area having no pin is provided between a sound start position and a sound end position.
The silent area is provided because the silent area need be arranged opposite to the vibrating valves when, for example, the rotation of the rotating drum body 3 is stopped to stop the sounding of the music box.
That is, if the rotating drum body 3 is stopped in the condition in which a pin and a vibrating valve for flicking the pin are in contact with each other, the pin and the vibrating valve are loaded on each other so that the pin and the vibrating valve may be deformed thereby causing deterioration of tone quality.
Further, a reference position of the rotating drum body, that is, a reference position indication (reference position mark) for indicating the sound start position of the music box, is formed in a substantially middle position in a direction of rotation, of the silent area.
The reference position indication is provided for indicating the sound start position of the music box and serves as a reference for determining the position relative to holding members (gears or end plates) for rotatably holding the rotating drum body at opposite ends of the rotating drum body.
When, for example, the holding element (such as a hole) for engaging/disengaging a stopper member to stop the sounding of the music box is provided at an end surface of the holding member (gear or end plate), the position of the hole relative to the silent area must be kept constant. This is because the silent area in the rotating drum body must be placed opposite to the vibrating valves when the rotating drum is stopped by the stopper member. Thus, a problem arises in that good sound cannot be produced if a mistake in the holding member mounting position is made when the holding members are combined with the rotating drum.
Further, if the holding element (such as a hole) of the holding member (gear or end plate) and the reference position indication are detected so that the two can be fitted to each other at a predetermined angle in a direction of rotation, automatic assembly of a rotating drum body including gears or end plates can be provided.
Incidentally, it is required that a high-grade music box be beautiful in appearance, because the music box is produced so that not only the rotating drum body is long but the internal structure can be seen from the outside.
Accordingly, though the rotating drum body is rotated to sound the music box, pins are flicked some time after the rotation of the rotating drum body on the basis of the silent area, rather than the pins being flicked soon after the rotation of the rotating drum body.
Also in the case where the sounding of the music box is terminated, the rotation of the rotating drum body is not stopped soon after but the rotation is stopped some time after the rotation of the rotating drum on the basis of the silent area to provide the lingering sound thereof. Thus, the listener's interest (expectation) is roused in between the sense of sight (rotation of the rotating drum) and the sense of hearing (silent area).
The reference position mark formed in a substantially middle position in the direction of rotation, of the silent area is formed by stamping on the basis of plastic working, printing paint, or the like.
Because the subject of the stamping is a cylinder surface in the case of the music box rotating drum body, a problem arises in that good stamping cannot be made, so that the mark may be unreadable. This is because there is a tendency of losing the circularity of the metallic pipe intense pressure is applied, to deform the sectional form of the pipe ellipsoidally. Furthermore, it is difficult to perform stamping of a large number of characters, because a large quantity of deformation of the pipe is exhibited.
Furthermore, in the case of printing using paint, the disadvantage of losing the circularity can be avoided, but a problem arises in that it is necessary to treat the surface of the pipe material with chemicals before printing. Otherwise, a problem arises in the durability of printing.